Luminol hydroxyl radical

Aqueous alkaline luminol solutions can be excited to chemiluminescence by pulse radiolysis, the only additional requirement being oxygen 119h The suggested mechanism is that hydroxyl radicals attacking luminol monoanions, followed by reaction of the luminol radical anion thus formed with oxygen ... 

MF effects on FA relatives and healthy donors. (Fanconi anemia is an autosomal recessive disease associated with the overproduction of free radicals, Chapter 31.) It has been shown earlier [215] that FA leukocytes produce the enhanced amount of hydroxyl or hydroxyl-like free radicals, which are probably formed by the Fenton reaction. It was suggested that MF would be able to accelerate hydroxyl radical production by FA leukocytes. Indeed, we found that MF significantly enhanced luminol-amplified CL produced by non-stimulated and PMA-stimulated FA leukocytes but did not affect at all oxygen radical production by leukocytes from FA relatives and healthy donors (Table 21.3). It is interesting that MF did not also affect the calcium ionophore A23187-stimulated CL by FA leukocytes, indicating the absence of the calcium-mediated mechanism of MF activity, at least for FA leukocytes. 

In addition to superoxide and hydroxyl radicals, luminol produces CL in the reaction with peroxynitrite [67], To discriminate between superoxide- and peroxynitrite-induced CL, the use of lucigenin-amplified CL has been recommended [68] because peroxynitrite does not interfere in this assay. Another way is to apply the inhibitors of peroxynitrite to distinguish between superoxide- and peroxynitrite-induced luminol CL. 

Oosthuizen and Greyling [93] recently investigated the possibility of using chemiluminescent methods for hydroxyl radical detection. These authors concluded that the lifetime of hydroxyl radicals (10 9 s) is too short to produce a meaningful level of CL. However, in the presence of carbonate the significant levels of luminol- and MCLA-amplified CL were observed supposedly due to Reaction (18), in which the formed much more stable radical C03- is capable of interacting with luminol or MCLA. 

The effect of the hydroxyl radical (HO ) on luminol chemiluminescence has also been intensively studied Although detailed mechauisms for the reactiou of hydroxyl radicals with hydrazides remaiu uuknowu, two differeut processes are assumed to be involved oxidation of the hydrazide group and addition of hydroxyl radical to the aromatic ring (Scheme 19) ° . 

The reaction between hydroxyl radical and luminol results in the quantitative formation of hydroxylated products, which are known to be radical scavengers (Scheme 19) °. The reduction of luminol radical anion by these species decreases the emission intensity, unless HO is generated rapidly in high concentrations . The emission observed under these conditions may be attributed to one-electron oxidation of luminol by hydroxyl radicals, yielding luminol radical anion, or by hydroxyl-mediated generation of potent one-electron oxidants from its reaction with bases. Moreover, the addition of HO to luminol or its monoanion results in an adduct able to react very rapidly with O2, yielding, in addition to hydroxylated luminol, superoxide (Scheme 19) °. 

Yildiz G, Demiryurek AT. Ferrous iron-induced luminol chemiluminescence a method for hydroxyl radical study. J Pharm Toxic Methods 1998 39 179-84. 

Iron dependent hydroxyl radical formation (assay I). The sample contained the following substances in lmL 50 mmol/L potassium phosphate buffer, pH 7.4 50 pmol/L luminol, 100 pmol/L Fe3+, 100 pmol/L EDTA, 100 pmol/L ascorbate, 500 pmol/L H2O2 and either the tested extract at the concentrations shown in Fig. 1 or a buffer as a control. The CL was measured using the flash assay option of the MultiUse program, every 50 milliseconds. 

The quenching of peroxidized luminol chemiluminescence by reduced pyridine nucleotides has been reported. Neither superoxide nor hydroxyl radical scavengers were found to quench the chemiluminescence of luminol in the presence of horseradish peroxidase and H2O2. Both chemi- and bio-luminescence of firefly luciferin have been investigated and a dioxetanone mechanism proposed for the light-producing pathway. ... 

Aluminium salts stimulated luminol-enhanced chemiluminescence production by human neutrophils (Stankovic and Mitrovic 1991). Kong et al. (1992) described an Al(lll) complex with O which was a stronger oxidant than 02 " itself and which may contribute to the adverse biological effects of Al(III). Aluminium can enhance hydroxyl radical production by iron, but it is not in itself capable of catalysing the generation of hydroxyl radical fi-om the Fenton or Haber-Weiss reactions (Gutteridge et al. 1985). Aluminium fadhtation of iron-mediated Upid peroxidation is dependent on substrate, pH (greater at pH 5.5 than 7.4), and alumi-... 

Several methods are used for the determination of the "active" zones in a vessel. These include optical (light diffraction), chemical, electrical, or mechanical (metal foil perforation), the measurement of local temperature increase (silicone-coated thermocouple), microdiffusion sensor, microvibration thermal sensor, microphones, or sonoluminescence.45 The principle of the latter consists of the oxidative degradation of luminol to aminophthalate under the action of the hydroxyl radical produced by water sonolysis. Aminophthalate is produced in an... 

Hydroxyl radicals and/or superoxide radical anions appear to be essential in the luminol reaction in aqueous solution (see p. 101) although not in an aprotic medium. 

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